M. Lampe and H. Rohling: “Aufwandsgünstige Verfahren zur Reduktion der Auβerbandstrahlung in OFDM-Funkübertragungssystemen” [Cost-Effective Method for Reduction of the Out-Of-Band Radiation in OFDM Wireless Transmission Systems], a lecture given at the OFDM technical conference in Braunschweig on Sep. 3, 1989, printed in the proceedings of the conference, refers to a transmitter for transmitting OFDM (orthogonal frequency division multiplexing) signals, in which a reduction of the amplitude variance reduces out-of-band radiation caused by the nonlinearity of the transmitter, by subtracting an additive correction signal from the OFDM signal to be transmitted. The correction signal is the difference between a predefined threshold and the amplitude values of the OFDM signal that lie above the threshold. If the amplitude of the OFDM signal is less than the threshold at a specific instant, then the amplitude of the correction signal at the specific instant is zero.
A method for correction of the amplitude variance is discussed in European Published Patent Application No. 735 731, in which generated partial signals are added with different signs, depending on amplitude statistics. In this manner, intervention in the coding is achieved. The additional information should be transmitted to the receiver, where it should be decoded. European Published Patent Application No. 743 768 discusses an envelope of a signal, which comprises many different signals, each modulated with frequency shift keying, being reduced by phase shift of these individual signals.